Note: Descriptions are shown in the official language in which they were submitted.
~6284
HIGH SEVERITY VISBREAKING
This invention relates to upgrading of feeds by
visbreaking, and more particularly, to a process for increasing
the severity of a visbreaking operation.
Feeds from a wide variety of sources have been subjected
to visbreaking (both thermal visbreaking and hydrovisbreaking)
to upgrade the feed by converting higher boiling materials to
lower boiling materials. In general, such feed contains at
least 25 volume percent of materials boiling above about
850F, which are derived from a wide variety of sources, and
the visbreaking operation is designed to produce lower boiling
materials from such heavier materials. In attempting to
upgrade feeds by a visbreaking operation, the severity of the
operation has generally been limited in that attempts to
operate visbreaking at higher severities results in unstable
products. Moreover, depending on the severity of the
visbreaking operation, coking and fouling of equipment may
occur during the visbreaking reaction, which further limits the
ability to increase the severity of the visbreaking operation.
Thus~ for a given feedstock, the greatest conversion could be
achieved by increasing severity; however, such increase in
severity may adversely affect product quality and/or the rate
of coke formation, whereby the ability to increase conversion
of increasing severity is limited.
~arious schemes have heen propos~d for increasing the
severity of a visbreaking operation. Thus, for example, U.S.
4?4~4~023 proposes to increase the severity of a visbreaking
operation by subjecting heavy product from the operation to a
L044350
~2962~3
- 2 -
solvent extraction step to produce, as separate fractions,
solvent extracted oil, resin and asphaltene, with the resin
fraction being recycled to the visbreaking operation to premit
an increase in severity. Such an operation uses a conventional
deasphalting solvent to produce a product fraction, which is
essentially free of asphaltenes. In this operation, in
general, about 40% or more of the feed to the deasphalting is
recovered as asphaltenes.
In accordance with the present inventiona there is
provided a procedure for upgrading heavy viscous materials by a
visbreaking operation by treating product from the visbreaking
to separate components which adversely affect product
stability, without removing all of the asphaltenes. Applicant
has found that the stability of product from a visbreaking
operation can be increased by removing certain materials from
the product, without the necessity of removing all of the
asphaltenes, whereby the severity of a visbreaking operation
may be increased.
Applicant has further found that if coking and fouling is
a problem during the visbreaking operation when operating at a
desired higher severity, a portion of the treated product may
be recycled to the visbreaking operation in an amount to rQduce
and/or eliminate the risk of coking and/or fouling during the
operation.
More particularly, in accordance with one aspect of the
present invention, a heavy viscous material is upgraded by a
visbreaking operation (either thermal or hydro-visbreaking) at
a severity such that the visbreaking product has a Shell Hot
Filtration number of greater than 0.25 (preferably at least
0.3), followed by treating of the product to separate a heavier
fraction therefrom and to provide a treated or remaining
product having a Shell Hot Filtration number of less than 0.25
(preferably less than 0.15), with the separated heavier
fraction being no greater than 15%~ by weight of the 650~F+
feed to the treating, on a diluent free basis, and preferably
not greater than 10% (most preferably not greater than 5%), all
L044350
~9~x~
- 3 -
by weight, of the 650F+ feed to the treating, on a diluent
free basis. The Shell Hot Filtration number is on the 650F+
fraction. The manner of obtaining the Shell Hot Filtration
number is reported in hereinafter Example 1 and the Shell Hot
Filtration number is a weight percent.
More particularly, applicant has found that it is possible
to increase the severity of a visbreaking operation, and to
provide a stable product, by treating all or portion of the
visbreaking product to separate certain materials from the
product or portion thereof, without removing all of the
asphaltenes. By increasing severity and by removing only
certain materials, rather than all of the asphaltenes, overall
yields are increased. Thus, the sever;ty of the visbreaking
operation is increased so that the visbreaking product has a
Shell Hot Filtration number in excess of 0.25, followed by
treating of all or a portion of the product to remove heavier
components to thereby reduce the Shell Hot Filtration number to
a value of less than 0.25, with the removed heavier components
being no greater than 15 weight percent of the diluent free
feed to the treating, whereby unstable components are separated
from the visbreaking product, without the necessity of removing
all of the asphaltenes.
The manner in which the visbreaking product is treated to
provide a treated product having a Shell Hot Filtration number
is dependen~ upon the product which is produced in the
visbreaking operation, which, in part, is dependent upon the
feed material to the visbreaking. Thus, the treatment is
directed toward removing materials which form a separate phase
in the reaction product, which separate phase is heavier
(higher specific gravity) than the main product phase.
In some cases, it may be possible to treat the product so
as to prov;de a Shell Hot Filtration number, as hereinabove
described, by physically separating a heavier separate phase
from the reaction product by techniques such as centrifugation,
filtration, gravity settling, etc., with centrifuging being
particularly preferred.
L044350
~1.2~6~84
In other cases, in order to provide a Shell Hot Filtration
number, as hereinabove described, it may be necessary to
enhance the separation of a separate heavier phase by use of a
promoter liquid or anti-solvent so as to reduce the solubil;ty
of the components which adversely affect product stability,
followed by physica7 separation of such components from the
product or product portion to provide a Shell Hot Filtration
number, as hereinabove described.
In still another case, it may be necessary to add a
diluent liquid, which does not significantly increase or
decrease the solubility of the components which ~orm a separate
phase in the reaction product, with the diluent liquid
functioning to reduce the viscosity of the product to a value
which permits physical separation of unstable components at the
required operating conditions.
In accordance with a particularly preferred embodiment,
the Shell Hot Filtration number is reduced to a value as
hereinabove described by centrifugation of all or a portion of
the visbreaking product, with or w;thout the addition of a
liquid, which functions as a diluent and/or anti-solvent.
As hereinabove indicated, all or a portion of the
visbreaking product may be treated so as to reduce the Shell
Hot Filtration number to a value as hereinabove described.
Thus, for example, the entire effluent from the visbreaker may
be treated, or in the alternative, as shown in the art, the
effluent from the visbreaker may be introduced into a flash
~one and/or distillation zone and/or a combination of a flash
zone and distillation zone to remove lighter materials, such as
gas oil and lighter components, from the product, with the
remaining heavier portion of the product then being treated to
reduce the Shell Hot Filtration number. Thus, the materials
which create an unstable product are primarily present in the
higher boiling portion of the visbreaking product, whereby the
visbreaking product, ei~her prior or subsequent to removal of
lower boiling materials, may be subjected to treatment to
reduce the Shell Hot Filtration number.
L044350
~LZ ~iZ 8~
The visbreaking product or portion thereof is generally
treated at a temperature of from 200F to 700F, and preferably
from 300F to 700F for the purpose of reducing the Shell Hot
Filtration number. In addition, the viscosity of the product
or portion thereof which is to be treated must be at a value
which permits separation of a heavier phase from the treated
product or product portion in the separation equipment. The
viscosity of the product during treatment is determined, in
part, by the method which is used for physically separating the
two phases. In general, the viscosity in the treating
equipment is in the order of from 50 centistokes to 0.1
centistokes, at the treating temperature. The treating
pressure may be in the order of from atmospheric pressure to
200 psig.
As should be apparent, in the case where a centrifuge is
used, as in the preferred embodiment, the viscosity of the
product introduced into the centrifuge must be at a value such
as to permit proper operation of the centrifuge at the
treatment temperature. As should be apparent, viscosity
increases with a decrease in the treatment temperature,
whereby, depending upon the temperature of operation, it may
not be necessary to add a diluting liquid to reduce viscosity
at the treatment temperature. In some cases, the liquid which
is added may, in addition to reducing viscosity, function as an
anti-solvent, as hereinabove described or as a cutter stock for
use of the product as a fuel oil.
As hereinabove described, in order to reduce the Shell Hot
Filtration number to a value, as hereinabove described, it may
be necessary to use an anti-solvent to provide controlled
rejection of additional components. In particular, the
anti-solvent provides for reducing the solubility of components
which adversely affect product stability to reduce the Shell
Hot Filtration number. The anti-solvent employed as well as
the amount thereof is such that no more than 15%, by weight, of
the diluent or solvent free feed to the treating is removed
from the feed to the treating as heavier components.
L~44350
~2~62~3~
- 6 -
Liqu;ds used as anti-solvents, in the case of the use of a
hydrocarbon liquid, have a Watson characterization factor which
characterizes such liquids as being more aliphatic than
aromatic, with the Watson characterization factor generally
being from 9-12. The liquid may be comprised of one or more
components; e.g., the promoter liquid may be a cycle oil or a
gas oil (350-650F. It is to be understood, however, that
liquids other than hydrocarbons may be employed for
anti-solvent properties, provided that such liquids provide a
controlled insolubilization of material as hereinabove
described.
Thus, as should be apparent, the visbreaking product or
product portion is treated in a manner so as to reduce the
Shell Hot Filtration number to values as hereinabove described,
after a visbreaking operation which is operated at a severity
which produces a visbreaking product having a Shell Hot
Filtration number in excess of 0.25. Moreover, such treatment
is effected in a manner which prevents rejection of all of the
asphaltenes present in the product in that applicant has found
that it is possible to provide a stable visbreaking product,
which is produced at a high severity, without rejecting all
asphaltenes.
In the case where the visbreakin~ operation is operated at
a severity such that there tends to be coking and/or fouling,
in accordance with the present invention, the high severity may
be maintained, without adverse fouling and/or coking, by
recycling a portion of the treated product to the visbreaking
operation. The product or product portion is treated as
hereinabove described to provide a stable visbreaking product,
and a portion of such stabilized visbreaking product is then
recycled to the visbreaking operation to reduce and/or
eliminate adverse coking and/or fouling.
The feeds which are subjected to a visbreakin~ operation
are feeds which are heavy and viscous, and which may be
obtained from a wide variety of sources, such as petroleum
sources; bitumens from tar sands, materials derived from coal
L044350
~LZ ~6 2 ~3~
sources such as coals, lignite, peat; materials derived from
oil shale; materials derived from a wide variety of petroleum
sources such as residuums resulting from atmospheric and/or
vacuum distillation of crude oil, heavy residues from solvent
extraction processes, and the like. Such materials are
generally comprised of a mixture of hydrocarbons, and are
characterized by an API gravity of less than 20 degrees. Such
feeds are generally known in the art, and no further details in
this respect are deemed necessary for a complete understanding
of the present invention.
In accordance with the present invention, a feed is
subjected to visbreaking at a high severity to produce a
product having a Shell Hot Filtration number in excess of 0.25.
In general, the visbreaking (whether thermal visbreaking or
hydrovisbreaking) is operated at a temperature of from 700F to
1000F, and a pressure of from 25 to 2000 psig. The severity
of the operation is generally sufficient to convert from 4% to
25%, by weight, of the fresh feed to 350F- material.
Depending on the feedstock, it is to be understood that higher
or lower severities may be obtained within the spirit and scope
of the invention.
The equipment which is employed for visbreaking may be of
a type known in the art; for example, a coil, or coil plus
soaking drum, etc. As hereinabove indicated, the visbreaking
may be effected thermally, or may by a hydrovisbreaking
operation, in which case, gaseous hydrogen or a donor liquid is
added to the feed material.
The product from the visbreaking may then either be
directly treated to reduce the Shell Hot Filtration number, or,
preferably, as hereinabove described, the product is subjected
to a distillation operation to separate lighter materials,
with the remaining heavier materials then being subjected to
treatment, as hereinabove described, to remove an insoluble
heavy phase and reduce the Shell Hot Filtration number.
L0~4350
~29628~
BRIEF ~ESCRIPTION OF THE DRAWING
The invention will be further described with respect to
the following drawing, wherein:
The drawing ;s a simplified schematic flow diagram of an
embodiment of the present invention.
Referring now to the drawing, a viscous feed, which is to
be subjected to visbreaking, in line 10, is combined with
recycle, if any, in line 11, and the combined feed in line 12
is introduced into a visbreaking unit, schematically generally
indicated as 13.
The visbreaking unit 13 maybe of a type known in the art
and may be comprised of a coil, or preferably a coil plus
soaking drum. The visbreaker is operated to provide a high
severity operation wherein the product recovered from the
visbreaker 13, in line 14 has a Shell Hot Filtration number in
excess of 9.25, and preferably in excess of 0.3. The Shell Hot
F;ltration number is determined on the ba~is of 650F+ material
in the product.
The product in line 14 is introduced into a separation
zone, schematically shown as 15, which may contain one or more
columns and/or other types of separation devices. In the
separation zone 15, the visbreaking product is separated to
recover, preferably as separate fractions, a C4-gas, a C5 to
350F gasoline fraction, and a 350F to 650F gas oil fraction.
Depending upon the products desired, the separation zone 15 may
be operated to recover a 650F+ fraction, which is then treated
in accordance with the present invention, or alternatively, the
separation zone 15 may be operated to recover a heavier gas oil
fraction which boils from 650F to 900F, and a heavier
fraction, which is a 900F plus fraction, which is then treated
in accordance with the present invention.
The heavy fraction recovered from separation zone 15
through line 16, as hereinabove noted, may be either a 650F+
fraction, or a 900F+ fraction. It is to be understood,
however, that the heavier fraction recovered through line 16 may
or may not include all of the components which boil above
L044350
i2~
g
650F. Thus, for example, it is possible to recover a 750F+
fraction and/or a 950F+ fraction through line 16.
The heavy fraction in line 16 is introduced into a
treating zone, schematically generally indicated as 17 to
separate heavier components therefrom and to reduce the Shell
Hot Filtration number and preferably also the P test number to
values as hereinabove described, without removing more than
15%, by weight of the materials introduced into the treating
zone 17 through line 16.
~epending upon the characteristics of the material in line
16, which is dependent upon the feed in line 10, as well as the
specific conditions for visbreaking, it may or may not be
necessary to add additional components to the treating zone 17
to enable removal of heavier components, as hereinabove
described, and thereby reduce the Shell Hot Filtration number
and increase without removing all of the asphaltenes.
Thus, for example, in one embodiment the heavier material
in line 16 is treated in treating zone 17 to recover heavier
components through line 18 and provide a remaining product in
line 19, without adding an extraneous material to the treating
zone 17. In such an embodiment, the remaining product in line
19, may be mixed with a cutter stock in line 21,as known in the
art, to provide a fuel oil product in line 22.
In another embodiment, the cutter stock for providing a
fuel oil mixture may be added to the treating zone 17 through
line 23, with such cutter stock functioning as a diluent to
reduce viscosity to a value effective for the treatment in
treating zone 17. Alternatively, a diluent other than a cutter
stock may be employed in line 23.
As a further embodiment, it may be necessary to employ an
an~isolvent ;n order to reduce the Shell Hot Filtration number,
as hereinabove described, without removing more than 15 weight
percent of the undiluted feed to the treating zone, as heavier
components through line 18. In such an embodiment, antisolvent
in line 24, which is comprised of fresh feed antisolvent in
line 25 and recycle antisolvent in line 26 is introduced into
L044350
1~628~
- 10 -
the treating zone 17 for reducing the solubility of a portion
of the components introduced through l;ne 16 to reduce the
Shell Hot Filtration number without removing more than 15
weight percent of the feed introduced through line 16. In such
an embodiment, a mixture of the remaining product and
antisolvent ;s recovered from treating zone 17 throu~h line 19,
and the mixture is introduced through line 27 into a solvent
recovery zone, schematically generally indicated as 28. In the
solvent recovery zone 28, solvent is recovered through line 26
for recycle, and remainin~ product is recovered through line
29, which may be diluted with cutter stock in line 21 for
subsequent use as a fuel oil in line 22.
The treating 70ne 17 is preferably comprised of one or
more centrifuges for effecting separation of the heavy
components; however, as hereinabove described, other separating
devices may be employed.
As hereinabove described, in some cases, when operating at
a high severity, it may be necessary to employ a portion of the
treated product, as recycle to the visbreaker in order to
reduce and/or eliminate fouling or coking which may occur at
such severities. As shown in the drawing, a portion o~ the
treated product may be recycled to the visbreaker through line
11. As should be apparent, the treated product portion, which
is recycled through line 11, may be obtained by treatment with
or without an antisolvent and/or with or without use of an
appropriate diluent.
Thus, as should be apparent, in accordance with the
pre~erred embodiment, a heavy fraction recovered from the
visbreaking, which boils above 650F, and which may be
comprised o~ all or a portion of the components which boil
about 650F is treated with or without a diluent or with or
without an antisolYent to reduce the Shell Hot Filtration
number to values as hereinabove described, without removing all
of the asphaltenes. In particular, in the treating to reduce
the Shell Hot Filtration number no more than 15 weight percent,
preferably no more than 10 weight percent, and more preferably
L044350
~296~8~
- 11 -
no more than 5 weight percent of the diluent free heavy
material subjected to treatment is separated from the product,
as a heavier phase.
Although the invention has been described with respect to
specific embodiments shown in the drawing, it is to be
understood that the scope of the invention is not to be limited
thereby. Thus7 for examp1e, although in the preferred
embodiment, the visbreaking product is separated into various
fractions, pr;or to treatment, it is possible to treat the
entire visbreaking product, prior to such separation. As
should be apparent, such an embodiment is less preferred in
that it would necessitate treating higher volumes of material.
As a further modification, in the case where the visbreaking
product is unstable in the lines and/or equipment prior to the
distillation, a portion of the treated product may be recycled
for mixing with the visbreaking product, prior to the
separation operation to improve stability.
It is also to be understood that various portions of the
overall system have not been described in detail; however, such
portions are deemed to be within the scope of those skilled in
the art from the teachings therein. l`hus, for example, the
visbreaking effluent, prior to separation, may be cooled by a
direct quench operation by using heavier material from the
separation zone and/or a portion of the treated product.
Although in accor~ance with a preferred embodiment, the
visbreaking product is employed for making a fuel oil, it is to
be understood that other uses are also within the spirit and
scope of the present invention.
The present invention will be further described with
respect to the following examples; however, the scope of the
invention is not to be limited thereby:
Example 1 - Shell Hot Filtration Test
This test is reported in J. Inst. Petroleum Vol. 37, No.
334 P. ~96-604, and the apparatus for performing the test is
shown therein.
L044350
~29628q~
- 12 -
Apparatus
1. Pressure filter.
2. 1/8" Hard felt disc.
3. Whatman No. 50 filter paper, 7 cm. ia.
4. 2 - 1000 ml. Erlenmeyr filtering flasks.
5. n-Heptane, Industrial Grade.
6. 1000 ~m Open end Mercury Manometer.
7~ Pour point test jar. or 4 oz. oil sample bottle.
8. 20 ml. graduate.
~. 250 ml. graduate.
10. Oil bath
11. 10 ml. pipette.
12. 25 ml. graduate.
Procedure
1. Place 50 gms of sample in pour test jar and suspend in
oil bath held at 212F for 24 hours. (This step to be
disregarded when testing material on an "as-received" basis.)
2. Dry filter paper in over at 220F for 1/2 hour. Store
papers in a dessicator, no dessicant, for 1 hour. Weigh to 4th
place.
3. Remove steam jacket from filter and place felt disc on
perforated plate. Flat part of plate goes down. Place weighed
filter paper on felt and connect vacuum. Apply enough vacuum,
approx. 30 mm Hg., to hold down paper. Attach steam jacket,
inlet on top.
4. Shut off vacuum and pass steam through jacket, make
sure jacket is hot. Weigh an empty 30 ml. beaker and add
approximately 10.3 gms of sample. This will be the gross
weight. The additional 0.3 gms of sample is for stickage in
beaker after pouring sample onto filter pad.
5. Pour 10.0+ 0.1 gms of sample (held at approximately
210F) on filter paper, ensuring that no sample runs off filter
shell wall.
6. Attach filter top tighten top 4 nuts and slowly apply
nitrogen to filter shell, increasing pressure in 2 lb.
increments to 15-20-30-40 psig until filtration starts. Amount
L044350
28/~
- 13 -
nf pressure required is dependent on density of samp1e.
Complete filtration should take 5-10 minutes for sample to pass
through.
7. Now re-weigh beaker plus stickage to get tar weight.
Subtract this weight from the previous gross weight to get net
weight of sample used for the f;ltration test.
8. When filtration is complete, indicated by passage of
nitrogen through filter and vacuum control bleed line, decrease
or increase amount of N2 to 20 ps;g for additional 5 minutes
until there is negligible drippage of sample through filter
paper and felt pad. Turn off N2 and vacuum and remove filter
~op .
9. If cake or paper is dry, shut off and detach steam
inlet and hook-up to cooling water for 10 minutes. Water inlet
can be at top or bottom.
10. When filter is cool, wash wall and cake with 2-10 ml
washings of n-heptane using 10 ml pipette and then with 9-20 ml
washings using 25 ml graduate (apply enough vacuum to maintain
a steady drip) approx. 80-100 mm Hg. or until filtrate is
20 clear. To suction off remaining n-heptane retained in felt pad
after each 20 ml wash, it is advisable to apply approximately
300 mm. Hg. vacuum or blocking off vac. bleed line with the
thumb for 10 seconds. Lighter gravity material will require
200 ml minimum of wash and 300 ml maximum for heavier gravity
material. After final 20 ml wash, apply maximum vacuum for 1
minute.
11. Remove vacuum and steam jacket. Any oil present on
paper whère jacket rim rested on paper should be washed away
with n-heptane. Leave paper on pad with maximum vacuum and
wash outer edge of paper with 10 ml n-heptane using
eye-dropper. Be careful to wash edge of paper so that
n-heptane will flow toward recessed groove of filter paper.
12. Remove paper and dry in oven at 220F for 1/2 hour and
cool in dessicator ~no dessicant) for 1 hour.
LQ4~350
~3~ 8
- 14 -
Calculation and Report
13. a. Calculate the Shell Hot Filtration Number of the
sample as follows:
Shell Hot Filtration Number - A(100)
W
A = weight of dry sludge, grams
W = weight of sample, grams
Precision
14. Re~ abilitY
Duplicate results by the same operator should not be
considered suspect unless they differ by more than 0.03 weight
percent absolute.
The present invention is particularly advantageous in that
the visbreaker may be operated at higher severities, without
the disadvantages heretofore encountered in the art; for
example, an unstable heavier product and/or severe fouling and
coking of equipment. By operating at a higher severity, the
yield of lighter produc~s is increased.
Moreover, in treating the heavier portion of the product
in accordance with the present invention, as compared to prior
art deasphalting techniques, the desired stability ;s obtained,
while increasing the yield of 650F~ material, which may be
employed, for example, as a stable fuel oil.
These and other advantages should be apparent to those
skilled in the art of the teachings herein.
In the present specification, and in the claims, in
describing the characteristics of the visbreaking product prior
to treatment, as well as the characteristics of the treated
product, with respect to the Shell Hot Filtration number, it is
to be understood that actual measurement of the Shell Hot
Filtration number, as part of the processing parameters, is not
necessary to bring a process within the scope of the appended
claims in that the Shell Hot F;ltration number defines a
characteristic of the feed or product.
Numerous modif;cations and variations of the present
invention are possible in light of the above teachings and,
L~44350
129~28a~
therefore, within the scope of the appended claims, the
invention may be practiced otherwise than as particularly
described.
L044350
